Low-fusing temperature porcelain, compositions, prostheses, methods and kits

ABSTRACT

A low-fusing temperature porcelain compositions, methods of use thereof on metal or porcelain substrates to form dental prostheses and kits therefor. Compositions of the invention have a fusing temperature of less than 800° C. and a coefficient of thermal expansion compatible with a substrate of metal or ceramic. Each composition includes, in weight percent of the composition, from 40 to 65 percent by weight SiO 2 , from 6 to 12 percent by weight Al 2  O 3 , from 6 to 12 percent by weight Na 2  O, from 5.5 to 10.50 percent by weight K 2  O, from 1 to 3 percent by weight Li 2  O, from 0.8 to 2.5 percent by weight CaO, from 0.8 to 4.0 percent by weight B 2  O 3  and from 0.1 to 0.8 percent by weight CeO 2 .

This is a continuation-in-part of U.S. provisional patent applicationSer. No. 60/012125 filed Feb. 23, 1996.

This is a continuation-in-part of U.S. provisional patent applicationSer. No. 60/012,125 filed Feb. 23, 1996.

FIELD OF THE INVENTION

The invention relates to porcelain compositions, dental prostheses,methods of use and kits thereof. More particularly the inventionprovides low-fusing temperature porcelain compositions, methods of usethereof on metal or porcelain substrates to form dental prostheses andkits therefor. The invention provides low-fusing porcelain paste opaque,low-fusing porcelain powder opaque, low-fusing porcelain crystals,low-fusing porcelain dentin and low-fusing porcelain transparent andopal enamels and low-fusing modifier porcelains including stains. Theinvention provides low-fusing porcelain having fluorescence, opalescenceand which hold their shape when heated to temperatures between 750° C.and 800° C. Low-fusing porcelain in accordance with a preferredembodiment of the invention is polishable to high luster, and thesmoothness of the polished porcelain results in at least about 50percent to 90 percent less wear on natural tooth enamel than polishedcoventional porcelain. Preferably an angle from a line tangent to apoint on a surface contour of a coating of porcelain composition of theinvention has less than a 20 percent change during heating from 23° C.to 800° C. Preferably a physical surface feature of a dental prosthesisformed from a low-fusing temperature porcelain composition of theinvention having a diameter (or longest dimension) of 0.5 mm retains adiameter (or longest dimension) of at least 0.25 mm after firing theprosthesis by heating from 23° C. to 800° C. and cooling from 800° C. to23° C. five times.

BACKGROUND OF THE INVENTION

A dental prosthesis often comprises a crown or bridge restoration inwhich a dental porcelain is fused to a supporting metal or ceramicsubstrate. Dental porcelains are generally a mixture of glass, ceramicopacifiers, pigments and the like. There are a number of keyconsiderations in selecting glass frit components to form a porcelainthat will be compatible with the selected substrate. For example, theporcelain must have a coefficient of thermal expansion close to but lessthan that of the substrate. Otherwise, a porcelain fused to thesubstrate will tend to crack and separate from its supporting structure.

It is an object of the invention to provide a porcelain composition thathas a low-fusing or processing temperature and a coefficient of thermalexpansion such that it can be used in combination with both metal andporcelain substrates in dental prostheses, useful in making, repairingor improving crowns and bridges for both conventional restorations tonatural dentition and to implant-based restorations.

Exemplary prior porcelain compositions are disclosed by Panzera in U.S.Pat. No. 4,481,036; Kosmos in U.S. Pat. No. 4,645,455; Kondo et al inU.S. Pat. No. 4,839,313; Heurtaux in U.S. Pat. No. 5,173,114; Komma etal in U.S. Pat. No. 5,281,563; Komma et al in U.S. Pat. No. 5,346,866.

SUMMARY OF THE INVENTION

A low-fusing temperature porcelain system for use in a dental prosthesisis provided. The porcelain system of the invention has components withcompositions which include from 40 to 65 percent by weight SiO₂, from 6to 12 percent by weight Al₂ O₃, from 6 to 12 percent by weight Na₂ O,from 5.5 to 12.5 percent by weight K₂ O (more preferably from 5.5 to10.5 percent by weight K₂ O), from 1 to 3 percent by weight Li₂ O, from0.8 to 2.5 percent by weight CaO, from 0.5 to 4 percent by weight B₂ O₃and from 0.1 to 0.8 percent by weight CeO₂. Preferably compositions ofthe invention include from 0.01 to 3.0 percent by weight P₂ O₅.

A preferred embodiment of the invention provides a composition whichincludes from 58 to 65 percent by weight SiO₂, from 6 to 12 percent byweight Al₂ O₃, from 7 to 12 percent by weight Na₂ O, from 5.5 to 18.0percent by weight K₂ O, from 1.5 to 3 percent by weight Li₂ O, from 1.2to 2.5 percent by weight CaO and from. 0.1 to 2.0 percent by weightCeO₂. Preferably the composition also includes from 0.01 to 3.0 percentby weight of P₂ O₅.

A preferred embodiment of the invention provides a composition whichincludes from 40 to 47 percent by weight SiO₂, from 5 to 8 percent byweight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from 9.0 to 10.5percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O, from 0.8 to3.0 percent by weight CaO, from 0.8 to 2.0 percent by weight B₂ O₃ andfrom 0.3 to 1.0 percent by weight CeO₂.

The porcelain of the invention has a fusing temperature of less than800° C. and a coefficient of thermal expansion compatible with asubstrate of metal or ceramic. Preferably, the coefficient of thermalexpansion is from about 11.5 to 13.4 ppm ° K⁻¹ from 30° to 430° C.!, andmore preferably 12.4 to 13.4 ppm ° K⁻¹ from 30° to 500° C.!

DETAILED DESCRIPTION OF THE INVENTION

The invention provides low-fusing temperature porcelain compositions,methods of use thereof on metal or porcelain substrates to form dentalprostheses and kits therefor. The invention provides a low-fusingtemperature porcelain system that is a mixture of oxides such that theresulting porcelain components have a fusing temperature of about 800°C. or less and a coefficient of thermal expansion of 11.5 to 12.5 ppm °K⁻¹ 30° to 430° C.!. The low-fusing porcelain may be employed in dentalcrowns, bridges, restorations and fixed dentures wherein it is fused toa substrate or coping of dental alloy copings, such as UltraCrown PDalloy distributed by Dentsply International (Ceramco), or fused to anappropriate all-ceramic substrate.

The compositional range for the low-fusing temperature dental porcelainsof the invention, having processing temperatures of less than about 800°C. and a coefficient of thermal expansion (CTE) of 11.6 to 12.6 ppm °K⁻¹ 30° to 430° C.! is a mixture of oxides having from 40 to 65 percentby weight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to 12percent by weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O, from 1to 3 percent by weight Li₂ O, from 0.8 to 2.5 percent by weight CaO,from 0.5 to 4 percent by weight B₂ O₃ and from 0.1 to 0.8 percent byweight CeO₂.

Liquids containing 98 to 100 percent by weight water are preferablymixed with porcelain compositions of the invention in from a one to oneweight ratio to a one (part liquid) to four (parts porcelain) weightratio and more preferably in a weight ratio of from one (part liquid) tothree (parts porcelain). For example, liquids contain 0.1 percent byweight of salts and/or preferably less than 0.5 percent by weight oforganic liquids and/or less than 0.5 percent by weight solids dissolvedin water are preferably mixed with porcelain compositions of theinvention in a one (part liquid) to three (parts porcelain) weightratio. Carving liquids for use with porcelain are preferred for use withcompositions of the invention for their ability to improve the handlingand carving of porcelain and to reduce slumping during build-up andcomplete burn off at low temperatures. Also, Finesse Opaque ModifierLiquid and Finesse Stain Liquid are preferred for use in mixtures withporcelain compositions of the invention.

The low-fusing porcelain compositions of the invention are preferred foruse in conjunction with non-precious or noble or high noble alloys whenused for porcelain-fused-to-metal crowns, bridges or dental prostheses.The low-fusing porcelain components of the system preferably containmixtures of frits, opacifiers and pigments in varied quantities tocreate an assortment of materials with a variety of fusion temperatures,translucencies and colors.

The low-fusing porcelain system of the invention is useful forfabricating porcelain-fused-to-metal restorations. All of the componentsfuse at temperatures approximately 200° C. lower than correspondingcomponents of conventional dental porcelains such as Ceramco II andCeramco II Silver porcelains. Preferably, each porcelain in the systemhas fluorescence. The use of these porcelains allows the dentaltechnician to create a more aesthetic restoration at a lowertemperature.

The low-fusing dentin and enamel porcelain compositions of the inventionare also easier to polish and yield smoother and less abrasive surfacesthan conventional porcelains. They contain fewer leucite crystals thanconventional porcelains. The porcelain composition of the inventionpossess superior handling characteristics, making the creation of arestoration easier for the dental technician.

The compositions of the invention provide a lower fusing temperaturethan standard porcelain system. The compositions of the inventionprovide low-fusing opaque porcelains having a fusing temperature of 775°C.-790° C., compared to 975° C. for a standard dental porcelain. Thecompositions of the invention provide low-fusing dentin porcelainshaving a fusing temperature of from 700° C. to 760° C. more preferablyfrom 720° C. to 740° C., compared to 920° C.-940° C. for a standarddentin porcelain.

The compositions of the invention provide thermal expansion compatiblewith a wider range of alloy compositions than Ceramco® II porcelain. Thecompositions of the invention provide low-fusing porcelains having athermal expansion coefficient of 12.1 ppm/° C. at 430° C., compared to12.5 ppm/° C. at 500° C. for Ceramco® II porcelain.

Compositions of the invention cause less wear against the opposingnatural teeth (dentition) than standard porcelain systems. Low-fusingdentin porcelain of a preferred embodiment of the invention provideswear of 5.6×10⁻² mm² compared to 18.2×10⁻² mm² for Ceramco porcelain ina three body wear test. Low-fusing dentin porcelain of a preferredembodiment of the invention has a Vickers hardness of 520 kg/mm²,compared to 620 kg/mm² for Ceramco II porcelain. The compositions of theinvention when utilized in forming dental prostheses are characterizedby having an easier polishability due to the reduced hardness comparedto conventional porcelain compositions.

Examples 1-5 describe preparation and use of preferred compositions ofthe inventions shown in Table 1 and characteristics of the resultingdental porcelain qualities are shown in Table 2.

Example 1

A low-fusing temperature porcelain having the composition indicated inTable 1, under Example 1, is made by combining and fusing oxides, thenpulverizing and blending with opacifiers and pigments. The resultingporcelain has a fusing temperature of less than 800° C. and a CTE ofabout 12.1 ppm ° K⁻¹ from 30° C. to 430° C. Samples of the resultingmaterial have the characteristics and properties shown in Table 2 forlow-fusing powder opaque when fired according to the schedule of Table3. The schedule for firing includes 3 minutes of drying, 3 minutes ofpreheating at 450° C. and heating from 450° C. to 785° C. under a vacuumof 29 inches of Hg at a rate of 90° C. per minute, at 765° C. the vacuumis released and heating is continued to 785° C.

Example 1A

Low-fusing porcelain compositions of Example 1A of the invention aremade in the same manner as Example 1, except having the compositionsindicated in Table 1, under Example 1A.

Example 2

Low-fusing porcelain compositions of Example 2 of the invention are madein the same manner as Example 1, except having the compositionsindicated in Table 1, under Example 2.

Example 2A

The procedure of Example 1 is followed except that the compositionindicated in Table 1A launder Example 2A is used in place of thecomposition in Table 1 under Example 1.

Example 3

A dental prosthesis having porcelain coated on metal is made by mixing 3parts of glass frit made as disclosed in Example 2 with one part oforganic gel to form a paste. The gel is composed of glycerine, butyleneglycol, diethylene glycol, preservative, cellulose, silica and water.The paste is then brushed onto metal base material to form a pastecoating. 1 part of crystals made as disclosed in Table 1 under Example 3are sprinkled onto the paste coating, for each 4 parts of paste coating,to form a paste with crystals embedded therein coating on the metalbase. The crystal-embedded paste coating is then dried for 5 minutes,then preheated for 5 minutes at 450° C., then fired by heating to 785°C. at a heating rate of 90° C. per minute while under a vacuum of 29inches of Hg between 450° C. and 765° C. and holding the temperature at785 for 1 minute to form a light refractive surface opaque porcelainlayer.

Example 4

3 parts of a glass frit having the composition in Table 1 under Example4 are mixed with 1 part of water to form a thick paste. The paste isbrushed onto the outer surface of the opaque porcelain layer of Example3.

Example 4A and 4B

The procedure of Example 4 is followed except that the glass fritcomposition in Table 1A under Example 4A or 4B is used in place of thatunder Example 4 in Table 1.

Example 5

The procedure of Example 4 is followed except that the glass frit usedis disclosed in Table 1 under Example 5.

DENTIN/ENAMEL LAYER

Example 5A

To the product of Example 3, an opaque porcelain layer, on aconventional dental ceramic palladium-gold-silver alloy, is applied 2parts of the product of Example 4 and then a discrete, separate additionof 1 part of the product of Example 5 and then drying at 100° C. for 5minutes, heating for 5 minutes at 450° C., followed by heating to 740°C. at a heating rate of 35° C. per minute while under a vacuum of 29inches of Hg between 450° C. and 720° C. to form a dentin enamel layeron a crown.

Example 5B

The procedure of example 4 is followed except that the glass frit usedis that disclosed in Table 1 under Example 5B.

Example 5C

The procedure of example 5A is followed, except that the glass frits ofExamples 3 and 4 are replaced with the glass frits disclosed in Table 1under Example 5B and Table 1A under Example 5C, respectively.

                                      TABLE 1                                     __________________________________________________________________________                            Example 2                                                     Example 1       LOW-FUSING      Example 3                                                                           Example 4                                                                          Example                                                                             Example 5B                   LOW-FUSING                                                                           Example 1A                                                                             PASTE OPAQUE                                                                          Example 2A                                                                            LOW-  LOW- LOW-  LOW-                         POWDER POWER OPAQUE                                                                           TRANSPARENT                                                                           PASTE OPAQUE                                                                          FUSING                                                                              FUSING                                                                             FUSING                                                                              FUSING                       OPAQUE MODIFIER ENAMEL  MODIFIER                                                                              CRYSTALS                                                                            DENTIN                                                                             OPAL                                                                                DENTIN                       (percent                                                                             (percent (percent                                                                              (percent                                                                              (percent                                                                            (percent                                                                           (percent                                                                            (percent             COMPONENTS                                                                            by weight)                                                                           by weight)                                                                             by weight)                                                                            by weight)                                                                            by weight)                                                                          by weight)                                                                         by weight)                                                                          by                   __________________________________________________________________________                                                             weight)              SiO.sub.2                                                                             45.3   52.0     42.7    57.1    62.7  62.7 62.0  60.8                 Al.sub.2 O.sub.3                                                                      7.1    7.8      6.6     8.2     11.2  8.4  8.9   8.6                  K.sub.2 O                                                                             10.1   11.4     9.5     9.7     8.4   5.9  6.1   12.2                 Na.sub.2 O                                                                            6.4    7.7      6.2     8.5     8.0   11.0 11.0  9.5                  Li.sub.2 O                                                                            1.6    1.7      1.5     1.5     2.0   2.4  2.4   1.7                  CaO     1.1    2.4      1.1     1.9     1.6   1.0  2.0   1.9                  CeO.sub.2                                                                             0.6    0.7      0.6     1.0     0.4   0.2  0.2   0.8                  MgO     --     --       --      --      1.6   2.7  2.7   0.3                  Tb.sub.2 O.sub.3                                                                      --     --       --      0.4     1.0   1.2  1.2   1.4                  B.sub.2 O.sub.3                                                                       1.1    1.3      1.1     1.3     2.0   3.5  3.5   1.4                  Y.sub.2 O.sub.3                                                                       0.6    0.7      0.6     0.7     0.8   --   --    --                   BaO     1.1    1.3      1.1     1.7     0.3   --   --    1.4                  TiO.sub.2                                                                             --     --       5.0     --      --    --   --    --                   ZrO.sub.2                                                                             18.0   7.0      15.0    --      --    --   --    --                   Y.sub.2 O.sub.3 --SiO.sub.2                                                           7.0    7.0      9.0     8.0     --    --   --    <1                   Pigments                                                                              10.0   35.0     10.0    15.0    --    <5   <1    <1                   __________________________________________________________________________

                                      TABLE 1A                                    __________________________________________________________________________             Example 2A Example 4A                                                                              Example 4B                                                                              Example 5C                                     LOW-FUSING LOW-FUSING                                                                              LOW-FUSING                                                                              LOW-FUSING                                     POWDER OPAQUE                                                                            DENTIN    DENTIN    OPAL ENAMEL                           COMPONENTS                                                                             (percent by weight)                                                                      (percent by weight)                                                                     (percent by weight)                                                                     (percent by weight)                   __________________________________________________________________________    SiO.sub.2                                                                              45.2       59        59        58.4                                  Al.sub.2 O.sub.3                                                                       6.1        7         7         8.0                                   K.sub.2 O                                                                              10.2       13.5      14.5      12.4                                  Na.sub.2 O                                                                             7.3        10.5      10.5      9.3                                   Li.sub.2 O                                                                             1.6        2         2         1.6                                   CaO      1.4        2         2         2.0                                   CeO.sub.2                                                                              0.7        1         1         1.1                                   Tb.sub.2 O.sub.3                                                                       0.7        1         --        1.1                                   B.sub.2 O.sub.3                                                                        1.4        2         --        1.5                                   Y.sub.2 O.sub.3                                                                        --         --        2         --                                    BaO      1.4        2         2         1.8                                   Pigments (0-15)     <5        <5        <1                                    ZrO.sub.2                                                                              24.0       <1        <1        <1                                    P.sub.2 O.sub.5                                                                        --         --        2.8       --                                    __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                 LOW-FUSING LOW-FUSING                                                                             LOW-FUSING                                                                            LOW-FUSING                                                                            LOW-FUSING OPAL AND                       POWDER OPAQUE                                                                            PASTE OPAQUE                                                                           CRYSTALS                                                                              DENTIN  TRANSPARENT ENAMEL           Examples     1          2        3       4       5                            __________________________________________________________________________    Physical Property                                                             Flexural Strength                                                                          65         109      --      84      73                           (MPa)                                                                         Chemical Solubility*                                                                       183        92       --      42      77                           (μg/cm.sup.2)                                                              Glass Transition                                                              Temperature (GTT) (°C.)                                                2 firings    460        500      486     465     464                          4 firings    464        500      484     462     461                          Thermal Expansion                                                             25° C. -- GTT                                                          2 firings    11.9       12.2     12.3    12.1    12.4                         (ppm/K)                                                                       Thermal Stability                                                             4 firings    12.4       12.2     11.9    12.0    12.3                         (ppm/K)                                                                       __________________________________________________________________________     *after 16 hours in boiling acetic acid.                                  

                                      TABLE 3                                     __________________________________________________________________________    Firing Schedules for Porcelain                                                __________________________________________________________________________    Composition of  Time    Vacuum  Idle  High                                    Example         (minutes)                                                                             Hold    Temperature                                                                         Temperature                             number Firing Program                                                                         Dry                                                                              Pre-Heat                                                                           (inches in Hg)                                                                        (°C.)                                                                        (°C.)                            __________________________________________________________________________    2, 3   Paste Opaque                                                                           5  5    0   29  450   785                                            and crystals                                                           1      Powder opaque                                                                          3  3    0   29  450   785                                     4 & 5  Dentin and Enamel                                                                      5  5    0   29  450   740                                     5B & 5C                                                                              Dentin and Enamel                                                                      5  5    0   29  950   780                                     __________________________________________________________________________                     Vacuum                                                                              Vacuum        High                                     Composition of   Start Stop   Heating                                                                              Temperature                              Example          Temperature                                                                         Temperature                                                                          Rate   Hold                                     number Firing Program                                                                          (°C.)                                                                        (°C.)                                                                         (°C./minutes)                                                                 (minutes)                                __________________________________________________________________________    2, 3   Paste Opaque                                                                            450   765    70     1                                               and crystals                                                           1      Powder opaque                                                                           450   765    90     0                                        4 & 5  Dentin and Enamel                                                                       450   720    35     0                                        5B & 5C                                                                              Dentin and Enamel                                                                       950   760    55     1                                        __________________________________________________________________________

The compositions of Examples 1-5 are fired according to the schedules inTable 3. Thus, the composition of Example 2 and 3 are fired by firstdrying for 3 minutes, then preheating for 3 minutes to 450° C. and thenheating from 450° C. to 785° C. under a vacuum of 29 inches of mercuryat a rate of 70° C. per minute. At 765° C. the vacuum is released andheating is continued to 785° C.

Example 6

A powder opaque kit container is provided which supports and encloseseighteen bottles each containing 15 g of the product of Example 1pigmented in sixteen Lumin™ of VITA Zahnfabrik shades, one AO shade andone BO shade; nine bottles of modifier porcelain each containing 15 g ofthe composition of Example 1A and pigmented White, Gray, Pink, Violet,Ochre, Yellow, Tan, Orange or Sienna; a bottle containing 120 ml ofcarving Liquid, sold by Ceramco, Inc.; and two Finesse Opaque ShadeFans. Each bottle has a threaded body and a threaded cap. Each shade fanhas eighteen porcelain chips. Each chip represents the shade of contentsof one of the bottles containing one of the pigmented compositions ofExamples 1 and 1A after firing as shown in Table 3.

Example 7

A paste opaque kit container is provided which supports and encloseseighteen syringes each having 2 ml of paste opaque porcelain, preparedas disclosed in Example 2 and pigmented in sixteen Lumin™ of VITAZahnfabrik shades, one AO shade and one BO shade; nine bottles ofmodifier porcelain each having 3 ml of the composition of Example 2A,mixed with gel and pigmented White, Gray, Pink, Violet, Ochre, Yellow,Tan, Orange, or Sienna; a bowl; a bottle containing 10 g of crystalshaving the composition of Example 3; a brush for application of thepastes; a bottle containing 15 ml of Opaque Modifier Liquid, sold byCeramco, Inc.; and two Opaque Shade Fans. Each shade fan has porcelainchips. Each chip represents one of the compositions of Example 2 andExample 2A in the eighteen syringes and nine bottles after beingdispensed and then fired as shown in Table 3.

Example 8

A prosthesis is prepared by forming an alloy metal into a dental toothcrown shape and oxidizing or degassing alloy according to the alloymanufacturer's instructions. The powder opaque porcelain composition ofExample 1 is then mixed with distilled water to a thin paste likeconsistency. The opaque paste is painted onto the alloy in a thin evenlayer, and condensed slightly to form an even coating on the outersurface of the alloy. The coated alloy is then fired according to Table3. A second coat of powder opaque composition of Example 1 is thenpainted onto the alloy metal to completely mask it. Opaque modifiers arethen applied. After condensing slightly to form an even coating outersurface the coated alloy is fired according to Table 3. The prosthesisproduct has a slight sheen after firing.

Example 8A

To 1 part of the product of Example 8 is applied, 2 parts of the productExample 4 having the composition shown in Table 1 and then 1 part of theproduct of Example 5 having the composition shown in Table 1. Thiscoating is then fired accordingly to Table 3 under Example 4.

Example 9

A prosthesis is prepared by forming an alloy metal into a dental bridgeshape, oxidizing or degassing the alloy according to the alloymanufacturer's instructions. Using a brush, the opaque paste compositionof Example 2 is applied to the alloy in a thin even layer. The brushcoated alloy is dried at 23° C. for 10 minutes and then fired accordingto Table 3. A second coat of the paste opaque porcelain pastecomposition of Example 2 is applied to the alloy metal to completelymask it. Opaque modifiers are then applied. Crystals are then sprinkledonto the second layer of the paste opaque and the coated alloy dentalbridge restoration is fired according to Table 3. The restoration has asandpaper or emery board appearance after firing.

Example 9A

To 1 part of the product of Example 9 is applied, 2 parts of the productExample 4 having the composition shown in Table 1 and then 1 part of theproduct of Example 5 having the composition shown in Table 1. Thiscoating is then fired accordingly to Table 3 under Example 4.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,including, from 40 to 65 percent by weight SiO₂, from 6 to 12 percent byweight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from 5.5 to 10.5percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O, from 0.8 to2.5 percent by weight CaO, from 0.5 to 4 percent by weight B₂ O₃ and 0.1to 0.8 percent by weight CeO₂ and from 0.01 to 3.0 percent by weight P₂O₅ and having a coefficient of thermal expansion of from about 11.5 to12.5 ppm ° K⁻¹ 30° to 430° C.!. Preferably the low-fusing temperatureporcelain composition further comprises from 0.5 to 1.5 percent byweight of Tb₂ O₃, from 10 to 20 percent by weight ZrO₂ and from 5 to 10percent by weight Y₂ O₃ --SiO₂.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising, from 40 to 65 percent by weight SiO₂, from 6 to 12 percentby weight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from 5.5 to 10.5percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O, from 0.8 to2.5 percent by weight CaO, from 0.5 to 4 percent by weight B₂ O₃ and 0.1to 0.8 percent by weight CeO₂ and at least 0.4 percent by weight of Y₂O₃.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,including a glass frit composition comprising from 40 to 65 percent byweight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to 12 percentby weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O, from 1 to 3percent by weight Li₂ O, from 0.8 to 2.5 percent by weight CaO, from 0.5to 4 percent by weight B₂ O₃, 0.1 to 0.8 percent by weight CeO₂, andfrom 0.5 to 3 percent by weight of MgO said glass frit compositionhaving a processing temperature of about 705° C. and a coefficient ofthermal expansion of from about 12 to 13 ppm ° K⁻¹ 20° to 500° C.!.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising a glass frit composition comprising from 40 to 65 percent byweight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to 12 percentby weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O, from 1 to 3percent by weight Li₂ O, from 0.8 to 2.5 percent by weight CaO, from 0.5to 4 percent by weight B₂ O₃ and 0.1 to 0.8 percent by weight CeO₂, saidglass frit composition having a processing temperature of about 705° C.and a coefficient of thermal expansion of from about 12 to 13 ppm ° K⁻¹20° to 500° C.! and from 40 to 47 percent by weight SiO₂, from 6 to 8percent by weight Al₂ O₃, from 8 to 12 percent by weight Na₂ O, from 9.0to 10.5 percent by weight K₂ O, from 1 to 2 percent by weight Li₂ O,from 0.8 to 1.5 percent by weight CaO, from 0.8 to 1.5 percent by weightB₂ O₃ and from 0.3 to 0.8 percent by weight CeO₂. Preferably thelow-fusing temperature porcelain composition further comprises from 0.5to 1.5 percent by weight of Tb₂ O₃, from 10 to 20 percent by weight ZrO₂and from 5 to 10 percent by weight Y₂ O₃ --SiO₂.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising a glass frit composition comprising from 40 to 65 percent byweight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to 12 percentby weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O, from 1 to 3percent by weight Li₂ O, from 0.8 to 2.5 percent by weight CaO, from 0.5to 4 percent by weight B₂ O₃ 0.1 to 0.8 percent by weight CeO₂, and from0.5 to 3 percent by weight of MgO said glass frit composition having aprocessing temperature of about 705° C. and a coefficient of thermalexpansion of from about 12 to 13 ppm ° K⁻¹ 20° to 500° C.!.

A preferred embodiment of the invention provides a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising a glass frit composition comprising from 40 to 47 percent byweight SiO₂, from 6 to 8 percent by weight Al₂ O₃, from 8 to 12 percentby weight Na₂ O, from 9.0 to 10.5 percent by weight K₂ O, from 1 to 2percent by weight Li₂ O, from 0.8 to 1.5 percent by weight CaO, from 0.8to 1.5 percent by weight B₂ O₃ and from 0.3 to 0.8 percent by weightCeO₂, said glass frit composition having a processing temperature ofabout 705° C. and a coefficient of thermal expansion of from about 12 to13 ppm ° K⁻¹ 20° to 500° C.!. Preferably the low-fusing temperatureporcelain composition further comprises from 0.5 to 1.5 percent byweight of Tb₂ O₃, from 10 to 20 percent by weight ZrO₂ and from 5 to 10percent by weight Y₂ O₃ --SiO₂.

A preferred embodiment of the invention provides a method of making adental prosthesis, comprising providing and shaping a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising, from 40 to 47 percent by weight SiO₂, from 6 to 8 percent byweight Al₂ O₃, from 8 to 12 percent by weight Na₂ O, from 9.0 to 10.5percent by weight K₂ O, from 1 to 2 percent by weight Li₂ O, from 0.8 to1.5 percent by weight CaO, from 0.8 to 1.5 percent by weight B₂ O₃ andfrom 0.3 to 0.8 percent by weight CeO₂ and heating said composition tobetween 740° C. and 800° C. to make a dental prosthesis.

A preferred embodiment of the invention provides a kit comprising acontainer support and at least three containers supported by saidcontainer support, each of said containers enclosing a low-fusingtemperature porcelain composition for use in a dental prosthesis,comprising, from 40 to 47 percent by weight SiO₂, from 6 to 8 percent byweight Al₂ O₃, from 8 to 12 percent by weight Na₂ O, from 9.0 to 10.5percent by weight K₂ O, from 1 to 2 percent by weight Li₂ O, from 0.8 to1.5 percent by weight CaO, from 0.8 to 1.5 percent by weight B₂ O₃ andfrom 0.3 to 0.8 percent by weight CeO₂.

Another preferred embodiment of the invention provides a low-fusingcomposition for use in a dental prosthesis, comprising form 40 to 65percent by weight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to12 percent by weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O,from 1 to 3 percent by weight Li₂ O, from 0.8 to 2.5 percent by weightCaO, from 0.5 to 4 percent by weight B₂ O₃, 0.1 to 0.8 percent by weightCeO₂, from 0.5 to 2 percent by weight Tb₂ O₃ and from 1 to 3 percent byweight MgO.

It should be understood that while the present invention has beendescribed in considerable detail with respect to certain specificembodiments thereof, it should not be considered limited to suchembodiments but may be used in other ways without departure from thespirit of the invention and the scope of the appended claims.

What is claimed is:
 1. A low-fusing temperature porcelain compositionfor use in a dental prosthesis, comprising, from 40 to 65 percent byweight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to 12 percentby weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O, from 1 to 3percent by weight Li₂ O, from 0.8 to 2.5 percent by weight CaO, from 0.5to 4 percent by weight B₂ O₃ and 0.1 to 0.8 percent by weight CeO₂ andfrom 0.01 to 3.0 percent by weight P₂ O₅ and having a coefficient ofthermal expansion of from about 11.5 to 12.5 ppm ° K⁻¹ 30° to 430° C.!.2. The porcelain of claim 1, having a fusing temperature of less than800° C. and a coefficient of thermal expansion compatible with asubstrate of metal or ceramic suitable for a dental prosthetic.
 3. Alow-fusing temperature porcelain composition for use in a dentalprosthesis, comprising, from 40 to 65 percent by weight SiO₂, from 6 to12 percent by weight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from5.5 to 10.5 percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O,from 0.8 to 2.5 percent by weight CaO, from 0.5 to 4 percent by weightB₂ O₃ and 0.1 to 0.8 percent by weight CeO₂ and from 0.5 to 2 percent byweight of Tb₂ O₃ and from 1 to 3 percent by weight MgO.
 4. A low-fusingtemperature porcelain composition for use in dental prosthesis,comprising, from 40 to 65 percent by weight SiO₂, from 6 to 12 percentby weight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from 5.5 to 10.5percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O, from 0.8 to2.5 percent by weight CaO, from 0.5 to 4 percent by weight B₂ O₃ and 0.1to 0.8 percent by weight CeO₂ and at least 0.4 percent by weight of Y₂O₃.
 5. A low-fusing temperature porcelain composition for use in adental prosthesis, comprising, from 58 to 65 percent by weight SiO₂,from 6 to 12 percent by weight Al₂ O₃, from 7 to 12 percent by weightNa₂ O, from 5.5 to 18.0 percent by weight K₂ O, from 1.5 to 3 percent byweight Li₂ O, from 1.2 to 2.5 percent by weight CaO, from 0.5 to 4percent by weight and from 0.1 to 2.0 percent by weight CeO₂.
 6. Alow-fusing temperature porcelain composition for use in a dentalprosthesis, comprising, from 40 to 47 percent by weight SiO₂, from 5 to8 percent by weight Al₂ O₃, from 6 to 12 percent by weight Na₂ O, from9.0 to 10.5 percent by weight K₂ O, from 1 to 3 percent by weight Li₂ O,from 0.8 to 3.0 percent by weight CaO, from 0.8 to 2.0 percent by weightB₂ O₃ and from 0.3 to 1.0 percent by weight CeO₂.
 7. The porcelain ofclaim 1, wherein said composition comprises from 60 to 65 percent byweight SiO₂, from 8 to 12 percent by weight Al₂ O₃, from 7 to 12 percentby weight Na₂ O, from 5.5 to 9.0 percent by weight K₂ O, from 1.5 to 3percent by weight Li₂ O, from 1.2 to 2.5 percent by weight CaO, from 1.5to 4.0 percent by weight B₂ O₃ and from 0.1 to 0.6 percent by weightCeO₂.
 8. A low-fusing temperature porcelain composition for use in adental prosthesis comprising, from 40 to 47 percent by weight SiO₂, from6 to 8 percent by weight Al₂ O₃, from 8 to 12 percent by weight Na₂ O,from 9.0 to 10.5 percent by weight K₂ O, from 1 to 2 percent by weightLi₂ O, from 0.8 to 1.5 percent by weight CaO, from 0.8 to 1.5 percent byweight B₂ O₃ and from 0.3 to 0.8 percent by weight CeO₂.
 9. Theporcelain of claim 7 further comprising from 0.5 to 3 percent by weightof MgO.
 10. The porcelain of claim 5 further comprising from 0.5 to 1.5percent by weight of Tb₂ O₃.
 11. The porcelain of claim 5 furthercomprising from 10 to 20 percent by weight ZrO₂.
 12. The porcelain ofclaim 7 further comprising from 5 to 10 percent by weight Y₂ O₃ --SiO₂.13. A low-fusing temperature porcelain composition for use in a dentalprosthesis, comprising a glass frit composition comprising from 40 to 65percent by weight SiO₂, from 6 to 12 percent by weight Al₂ O₃, from 6 to12 percent by weight Na₂ O, from 5.5 to 10.5 percent by weight K₂ O,from 1 to 3 percent by weight Li₂ O, from 0.8 to 2.5 percent by weightCaO, from 0.5 to 4 percent by weight B₂ O₃, 0.1 to 0.8 percent by weightCeO₂, and from 0.5 to 3 percent by weight of MgO said glass fritcomposition having a processing temperature of about 705° C. and acoefficient of thermal expansion of from about 12 to 13 ppm ° K⁻¹ 20° to500° C.!.
 14. The low-fusing temperature porcelain composition for usein a dental prosthesis of claim 13, wherein said composition comprisesfrom 60 to 65 percent by weight SiO₂, from 8 to 12 percent by weight Al₂O₃, from 7 to 12 percent by weight Na₂ O, from 5.5 to 9.0 percent byweight K₂ O, from 1.5 to 3 percent by weight Li₂ O, from 1.2 to 2.5percent by weight CaO, from 1.5 to 4.0 percent by weight B₂ O₃ and from0.1 to 0.6 percent by weight CeO₂.
 15. A low-fusing temperatureporcelain composition for use in a dental prosthesis, comprising a glassfrit composition comprising from 40 to 47 percent by weight SiO₂, from 6to 8 percent by weight Al₂ O₃, from 8 to 12 percent by weight Na₂ O,from 9.0 to 10.5 percent by weight K₂ O, from 1 to 2 percent by weightLi₂ O, from 0.8 to 1.5 percent by weight CaO, from 0.8 to 1.5 percent byweight B₂ O₃ and from 0.3 to 0.8 percent by weight CeO₂, said glass fritcomposition having a processing temperature of about 705° C. and acoefficient of thermal expansion of from about 12 to 13 ppm ° K⁻¹ 20° to500° C.!.
 16. The low-fusing temperature porcelain composition for usein a dental prosthesis of claim 14 further comprising from 0.5 to 1.5percent by weight of Tb₂ O₃.
 17. The low-fusing temperature porcelaincomposition for use in a dental prosthesis of claim 15 furthercomprising from 10 to 20 percent by weight ZrO₂.
 18. The low-fusingtemperature porcelain composition for use in a dental prosthesis ofclaim 15 further comprising from 5 to 10 percent by weight Y₂ O₃ --SiO₂.19. A method of making a dental prosthesis, comprising:providing andshaping a low-fusing temperature porcelain composition for use in adental prosthesis, comprising, from 40 to 47 percent by weight SiO₂,from 6 to 8 percent by weight Al₂ O₃, from 8 to 12 percent by weight Na₂O, from 9.0 to 10.5 percent by weight K₂ O, from 1 to 2 percent byweight Li₂ O, from 0.8 to 1.5 percent by weight CaO, from 0.8 to 1.5percent by weight B₂ O₃ and from 0.3 to 0.8 percent by weight CeO₂ andheating said composition to between 740° C. and 800° C. to make a dentalprosthesis.
 20. The method according to claim 19, wherein the glass fritis fused to a ceramic substrate to form the dental prosthesis.
 21. Themethod according to claim 19, wherein the glass frit is fused to aceramic or metal substrate to form the dental prosthesis.
 22. The methodof claim 19 wherein said composition comprises from 60 to 65 percent byweight SiO₂, from 8 to 12 percent by weight Al₂ O₃, from 7 to 12 percentby weight Na₂ O, from 5.5 to 9.0 percent by weight K₂ O, from 1.5 to 3percent by weight Li₂ O, from 1.2 to 2.5 percent by weight CaO, from 1.5to 4.0 percent by weight B₂ O₃ and from 0.1 to 0.6 percent by weightCeO₂.
 23. A kit comprising a container support and at least threecontainers supported by said container support, each of said containersenclosing a low-fusing temperature porcelain composition for use in adental prosthesis, comprising, from 40 to 47 percent by weight SiO₂,from 6 to 8 percent by weight Al₂ O₃, from 8 to 12 percent by weight Na₂O, from 9.0 to 10.5 percent by weight K₂ O, from 1 to 2 percent byweight LiO, from 8 to 12 percent by weight CaO, from 0.8 to 1.5 percentby weight B₂ O₃ and from 0.3 to 0.8 percent by weight CeO₂.
 24. The kitof claim 23 wherein said composition comprises from 60 to 65 percent byweight SiO₂, from 8 to 12 percent by weight Al₂ O₃, from 7 to 12 percentby weight Na₂ O, from 5.5 to 9.0 percent by weight K₂ O, from 1.5 to 3percent by weight Li₂ O, from 1.2 to 2.5 percent by weight CaO, from 1.5to 4.0 percent by weight B₂ O₃ and from 0.1 to 0.6 percent by weightCeO₂.
 25. The kit of claim 23 wherein each of said containers is asyringe.
 26. The kit of claim 23 wherein each of said containerscomprises a threaded cap and a threaded base.